1. Field of the Invention
This invention relates to a method of and an apparatus for producing metals with improved corrosion resistance. More particularly, the invention relates to a method of and an apparatus for producing steel and iron powder with improved corrosion resistance. In addition, this invention relates to a method and apparatus for processing iron powder to produce a magnetic substance.
2. Description of Related Art
Conventionally, attempts have been made to produce metals that are resistant to corrosion and climatic conditions, such as precipitation and humidity. For example, small amounts of rust have been allowed to form on a surface of the metal in an attempt to form a protective layer or barrier on the metal. In addition, metals have been coated with a magnetic substance to resist corrosion. Also, anticorrosion paints have been developed for being painted on the surface of the metal to protect the metal from corrosion. However, the following disadvantages are associated with above conventional techniques.
In particular, the protective layer or barrier of rust discussed above, may be produced by exposing the metal to the atmosphere. This type of rust is produced when the metal is exposed to rain or water and is called red rust. If the metal includes iron, for example, the particular type of red rust produced is lepidocrocite(.gamma.-FeOOH) and goethite (.alpha.-FeOOH). When this red rust dries, it changes into a black rust. The particular type of black rust produced primarily comprises triiron tetroxide (Fe.sub.3 O.sub.4), namely magnetite. However, the types of rusts discussed above and produced in the manner discussed above are large crystals rusts. Repeated wetting and drying of the metal causes the large crystal rusts to gradually spread and erode the metal. Naturally, as the rust continues to corrode the metal it becomes weaker.
Japanese Patent Provisional Publication No. 6-264256 discloses painting steel with an anticorrosion paint in a series of stages over a month long period. However, this is time consuming and extremely expensive. Moreover, with the use of an anticorrosion paint, additional work and time are necessary to paint an intricate product or the interior of a hollow tube, for example.
In addition, Japanese Patent Provisional Publication No. 6-143490 discloses painting the surface of steel material with paint mixed with triiron tetroxide. However, as discussed above, it proves to be impracticable to paint certain structures. For example, it is especially difficult to paint a welded structure, an electrically welded tube or a seamless tube.
Japanese Patent Provisional Publication No. 6-150813 discloses forming an indissoluble film on a mask frame for a shadow mask of a cathode-ray tube. However, to produce the indissoluble film, the mask frame must be processed in oxidizable air heated between 550.degree. C. and 650.degree. C. Therefore, it is impossible to use this process on a typical steel construction, for example, an electric welded tube, a seamless tube or a bent tube. Furthermore, to process, a magnetic material, for example, from iron powder by this process would be expensive because the iron powder would need to be heated to at least 600.degree. C. or higher and must be processed in the oxidizable air for an extended period of time. Specifically, the particular types of magnetic materials considered to be processed from the iron powder include triiron tetroxide (Fe.sub.3 O.sub.4) or diiron trioxide (.gamma.-Fe.sub.2 O.sub.3).
Finally, attempts have been made to clean the rust off of metal. For example, attempts have been made to clean steel by using a chlorine hydrocarbon solution such as a methylene chloride solution. To do so, however, the structure, such as a semiconductor or steel plate, must be immersed and then soaked in the methylene chloride solution, which may cause damage to the structure itself.